1. Field of the Invention
Embodiments of the present invention relate generally to the field of memory devices and, more particularly, to resistive random access memory (RRAM) devices.
2. Description of the Related Art
Electronic devices, such as computer systems, are often employed in numerous configurations to provide a variety of computing functions. For instance, computing speeds, system flexibility, applications, and form factor are typically some of the characteristics considered by design engineers tasked with the development of computing systems and their respective components. Often, such computing systems may include one or more memory devices which may be used to store applications (including program files and data) which may be accessible by other system components, such as one or more processors (e.g., CPU) or peripheral devices. By way of example, such memory devices may include volatile memory devices, such as dynamic random access memory (DRAM), or non-volatile memory devices, or a combination of both.
Non-volatile memory devices may include read-only memory (ROM), magnetic storage, flash memory, resistive random access memory (RRAM), and so forth. In particular, RRAM has become increasing popular due at least in part to its faster write/erase cycles (on the order of nanoseconds (ns)) and lower power consumption relative to conventional DRAM and flash memories, as well as its potential for use in high density memory devices, such as memory devices having memory cells fabricated at nanoscopic dimensions. RRAM is a general classification that may include memory devices based on: (1) oxygen vacancy switching materials, such as binary transition metal oxides (TMO), mixed valence oxides (MVO), and/or complex/conductive metal oxides (CMO) (e.g., providing for filamentary or area-distributed (interfacial) conductive pathways), (2) conductive-bridging RAM (CBRAM) and/or programmable metallization cell (PMC), and (3) phase change memory (PCRAM or PCM). RRAM devices may include an array of memory cells, wherein each memory cell includes first and second electrodes separated by an active material, which may have variable resistive properties and be capable of being switched between different states of electrical resistivity. For instance, the active material, which may include transition-metal oxides and/or chalcogenides, may transition between a high resistive state (an “OFF” state) and a low resistive state (an “ON” state) based upon an applied voltage. In some cases, when the active material transitions to the ON state in response to the applied voltage, conductive pathways, which may resemble a filament or may be area-distributed (e.g., interfacial), may be formed within the active material, thus providing a conductive path (e.g., a short circuit) between the electrodes of the RRAM memory cell. Removing the applied voltage or applying a different voltage (depending on the type of active material being used), may cause the conductive path to break or dispel, thus disconnecting the RRAM memory cell and returning it to the OFF state.
Further, as the development of non-volatile memory technologies, including RRAM, continues to trend towards smaller scaling dimensions (e.g., nanoscales), bulk deviating material and transport properties are often encountered. This may result in increasing cell-to-cell random variability due, for example, to continuum behavior breakdown and quantum effects that may become more apparent at such low dimensions. Accordingly, control of the formation of conductive current pathways through variable resistance materials is often recognized as one of several challenging aspects in the design of resistive memory devices and, particularly, resistive memory devices at nanoscopic dimensions.
Embodiments of the present invention may be directed to one or more of the problems described above.